Cardiac disease is the leading cause of death for men and women in the United States and accounts for at least 30% of deaths worldwide. Although recent medical advances have resulted in improvements in the diagnosis and treatment of complex cardiac diseases, the incidence of premature morbidity and mortality remains large, at least in part due to a dearth of accurate in vivo and in vitro estimates of patient-specific parameters indicative of a patient's anatomy, physiology, and hemodynamics.
Medical imaging-based techniques, such as myocardial perfusion imaging (MPI), may be used in clinical and pre-clinical settings to characterize the severity of stenosis (e.g., coronary stenosis, cerebral artery stenosis, etc.). Perfusion scanning may be implemented in a variety of ways, including as ultrasound perfusion, computed tomography (CT) perfusion, magnetic resonance (MR) perfusion, and nuclear medicine (NM) perfusion. The MPI procedure may be used to identify perfusion defects in rest and/or stress-induced images of the heart. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are two types of NM perfusion that have been used.
For single vessel disease, perfusion scanning may be sufficient to identify a culprit lesion responsible for causing an observed perfusion defect, and the culprit lesion may then be treated, for example, by percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) intervention, or another form of treatment. However, perfusion scanning techniques are not well suited to identifying culprit lesions in multi-vessel disease or in cases involving balanced ischemia (e.g., with left main disease in conjunction with other stenosis) since perfusion imaging provides relative perfusion values in overlapping perfusion territories that may be associated with more than one main vessel. As a result of the overlap, isolation of the hemodynamically significant lesion is difficult. Moreover, unless the culprit lesion is identified and differentiated from other lesions that may be present, the culprit lesion may not be properly treated.